In a typical rail vehicle (hereinafter, called a “vehicle”), a traction motor (hereinafter called a “motor”) is mounted on a bogie arranged below the vehicle body, and the rotative force of this motor is transmitted to the vehicle wheels through a coupling and a gearwheel device to move the vehicle. The construction of a conventional motor of this type is as shown in FIG. 14. The conventional motor shown in FIG. 14 has a cylindrical frame 1 constituting a fixed member, and a bearing bracket 2 is mounted on one end side of this frame 1, a housing 3 is mounted on the central portion of the other end side of the frame 1, and bearings 4, respectively provided at the central portions of the bearing bracket 2 and the housing 3 rotatably support both end portions of a rotor shaft 6. A rotor core 7 is fixed on the central portion in the axial direction of the rotor shaft 6, rotor bars 8 are embedded in a large number of respective grooves formed at the outer circumference side of the rotor core 7, the both end portions of the rotor bars 8 project from the rotor core 7, and these projecting potions are integrally connected by ring-shaped end rings 9, 9, respectively, to thereby form a cage rotor of an induction motor. The rotor core 7 is provided with a plurality of ventilation passages 7a passing therethrough in the axial direction, and the rotor core 7 is fixed by means of core holders 10, 10 having the similar ventilation passages.
A cylindrical stator core 11 is mounted on the inner circumference portion of the frame 1, and stator coils 12 are accommodated in a large number of respective grooves formed at the inner circumference side of this stator core 11. The coil end portions of these stator coils 12 are projecting from both sides of the stator core 11.
An air gap 13 is formed between the inner circumference surface of the stator core 11 and the outer circumference surface of the rotor core 7. A drive shaft portion 6a of the rotor shaft 6 projects outside the motor. A coupling for coupling with a drive gearwheel device is mounted on this projecting portion of the drive shaft portion 6a. A ventilation fan 14 is mounted on a portion of the rotor shaft 6 within the motor. The ventilation fan 14 has a plurality of vanes 14a arranged radially from the center of its axis of rotation. A plurality of exhaust ports la are provided along the circumferential direction at portions in this frame 1 facing the outer circumference portion of this ventilation fan 14. An air intake port 1b is provided above the side opposite to the drive side of the frame 1, a ventilation filter 15 is mounted so as to cover this air intake port 1b, and a filter 15a for capturing dust is mounted on the external air intake portion of this ventilation filter 15.
Mounting arms (not shown) provided on the frame 1 of the entire motor shown in FIG. 14 are fixed by means of bolts to the bogie frame, and the rotative force of the motor is transmitted from the drive device to the vehicle wheels through a coupling connected to the drive shaft 6a portion of the rotor shaft, to thereby move the vehicle.
When this motor is operated, as heat is generated by the stator coils 12 and the rotor bars 8, cooling is performed by passing external air through the interior of the motor. Rise in temperature of the motor is suppressed by this cooling. This cooling action is as follows.
During the operation, the ventilation fan 14 is rotated together with the rotor shaft 6, causing the air within the motor to be discharged outside the motor from the exhaust ports 1a, and thereby external air is sucked into the motor from the air intake port 1b. The external air flows into the motor from the air intake port 1b through the ventilation filter 15, and then flows to the ventilation fan side through the ventilation passages 7a of the rotor core and the air gap 13 between the outer circumference of the rotor core 7 and the inner circumference of the stator core 11, and is discharged outside the motor from the exhaust ports 1a by rotation of the ventilation fan 14.
External air is circulated in the motor in this way, and thereby the rotor bars 8, the stator coils 12, the bearings 104, 105 and the grease to lubricate these are cooled so that the rise in temperature thereof does not exceed the allowable temperature.
Large quantities of dust entrained during vehicle running are present in the external air around a motor that is mounted on an under floor bogie of an electric car or the like, and the external air which is taken in is under a severely polluted environment. Consequently, in the motor according to the conventional example shown in FIG. 14, although an attempt was made to clean the external air taken into the motor by capturing dust with the filter 15a of the ventilation filter 15, but as the gradual blockage of the filter 15a took place with the continuous operation and the amount of ventilation within the motor decreased, the periodic cleaning/maintenance of the filter was therefore required at short intervals. In addition, there was a technical problem that the dust which had passed through the filter 15a attached to and piled up in the motor and thereby the expenditure of a very considerable amount of labor was required for cleaning it.
In order to solve this problem, in recent years, the development of fully enclosed motors with outer fans has been promoted.
A construction of an embodiment of such a fully enclosed motor with outer fans will be described with reference to FIG. 10 and FIG. 11. FIG. 10 is a sectional view of a fully enclosed motor with outer fans, and FIG. 11 is a ¼ figure showing the section at a B-B portion of a stator core 211 in FIG. 10. The same numbers are given to the same component names as in FIG. 14, and the description thereof will be omitted.
As shown in FIG. 10, in a conventional fully enclosed motor with outer fans, core holders 211a, 211a are attached to the both sides of the stator core 211. Between the core holders 211a, 211a at the both sides, a plurality of connecting plates 211b are attached to portions of the whole outer circumference of the stator core 211 (Refer to FIG. 11). A plurality of ventilation passages 211c are made at the outer circumference side of the stator core 211. The rotor core 7 and a ventilation fan 214 having vanes 214a and 214b which are attached to the both faces of a fan main plate 214c radially from the axis of rotation are attached to the rotor shaft 6.
A plurality of external air intake ports 202a are made circumferentially at the side face portions of a bearing bracket 202 in which the bearing 4 to support the rotor shaft 6 is provided at the central portion. The bearing bracket 202 is attached to the core holder 211a through a connecting bracket 203. A fixed bracket 204 is attached to the core holder 211a of the other end of the stator core 211, and the bearing 5 is arranged at its central portion through the housing 3 to support the rotor shaft 6.
A ventilation passage 203a which leads to the ventilation passages 211c of the stator core 211 is made in the connecting bracket 203. Cooling wind flows in from a plurality of the external air intake ports 202a which are circumferentially provided at the side face portions of the bearing bracket 202 by the vane 214a of the fan 214, and is opened to outside air from a ventilation passage 204a of the fixed bracket 204 arranged at the other end.
A ventilation passage 203b which leads to an external heat exchanger 20 is also arranged in the connecting bracket 203, and a ventilation flow passage is made in which the air in the motor generated by the vanes 214b of the ventilation fan 214 enters again into the motor through a ventilation passage 204b provided in the fixed bracket 204 arranged at the other end without touching with external air. In the construction of the ventilation route like this, as a minute gap L0 (so-called labyrinth) is made between the inner circumference portion of the connecting bracket 203 corresponding to the outer circumference portion of the ventilation fan 214 and the fan main plate 214c of the ventilation fan 214, the construction that the ventilation air generated by the vanes 214a of the ventilation fan 214 and the ventilation air generated by the vanes 214b of the ventilation fan 214 do not mix with each other is used, that is, the motor is constructed such that the cooling wind inside the motor and the cooling wind outside the motor are used separately. In addition, in the following description of the motor, the inside of the motor and the outside of the motor indicate the inner portion and the outer portion which are partitioned by this minute gap, respectively.
A cooling method for the motor constructed like this is as follows. The cooling wind which has entered from the air intake ports 202a by the vanes 214a of the fan 214 passes through the ventilation passage 203a of the connecting bracket 203, passes through the ventilation passages 211c and is discharged to external air from the ventilation passage 204a of the fixed bracket 204. As a result, the heat generated in the coil 12 is cooled through the stator core 211.
There is cooling wind that the air inside the motor passes through the ventilation passage 203b of the connecting bracket 203, and returns to the inside of the motor from the ventilation passage 204b of the fixed bracket 204 via the heat exchanger 20, and this circulating wind is cooled with a heat exchanging operation between the heat exchanger 20 and the external air which enters from the air intake ports 202a by the fan main plate 214c of the fan 214, and the cooled cooling wind passes through the ventilation passages 7a and the air gap 13 to thereby cool the rotor bars 8 directly or via the rotor core 7. In addition, the air which has entered inside the motor is discharged again from the vanes 214b of the fan 214 to circulate inside the motor.
The circulation wind inside the motor cools not only the rotor bars 8 but the coils 12, the bearings 4, 5 and the grease and so on. Cooling winds flow separately through the respective ventilation passages inside the motor and outside the motor like this, causing the motor to be cooled efficiently, and the stator coils 12 and the rotor bars 8 do not touch external air and are not polluted, the inside of the motor is not polluted, and thereby a fully enclosed type motor in which internal cleaning is not required can be provided (Refer to Patent Document 1, for example).
Next, a problem restricted for a rail vehicle will be described. FIG. 12 and FIG. 13 show a general state that a motor for a vehicle is mounted inside a bogie, and FIG. 12 is a plan view seen from the upper face, and FIG. 13 is a side sectional view of a section CC portion of FIG. 12 seen from the side direction.
A motor 301 is mounted on a mounting seat 305 provided at a beam 304 of a bogie 303 through an upper mounting nose 302 and lower mounting feet 302a. A drive shaft 306 of the motor 301 is directly coupled with a gear shaft 308 of a gearwheel device via a coupling 306a. Gears (not shown in the drawings) are mounted to the gear shaft 308 and an axle 309, respectively, and engage with each other so that the rotative force of the motor is transmitted to the axle 309. A case 307 for the gears is filled with lubricant agent.
The rotative force transmitted to the axle 309 causes the wheels 310, 310 mounted on the axle 309 to rotate. As a result, a mechanism that a vehicle body 313 mounted on the bogie 303 moves while rolling on rails 311 is made. The axle 309 is rotatably fitted on the bogie 303 via bearings 312, 312. The motor 301 of FIG. 13 is shown by a sectional view so that the inside portion can be understood.
In the bogie construction like this, Ls is a size of a gap between the wheels 310, 310, and it is necessary to arrange the motor 301 within a range of a size Ld which is obtained by subtracting width sizes of the gear case 307 and the coupling 306A from this size Ls. That means, the motor 301 has a very limited size restriction. The magnitude of the output power of the motor 301 is determined by an outer diameter D of the stator core and a length L of the stator core (also equal to a length of the rotor). The outer diameter D of the stator core is shown in FIG. 10 and FIG. 13.
The length L of the stator core is shown in FIG. 10. As Ld is obtained by adding the other constituent members to the length L of the stator core, the other constituent members except the core are important in constituting the motor.
In a conventional fully enclosed type motor, because the heat exchanger 20 was to be added compared with a usual motor, and the vanes 214B of the heat exchanging fan 214 to flow the wind circulating inside the motor were provided, there was a problem that the construction was complicated and the cost was increased. In addition, there was the restriction for a motor for a vehicle with respect to the size of the motor as described above, it was necessary that the size of the motor in the longitudinal direction did not become large.